Use of chelating agents to improve color and color stability of petroleum distillate



USE or CHELATING AGENTS TO IMPROVE COLOR AND COLOR STABILITY OF PETROLEUM DIS- TILLATE Christopher P. Stark, Bartlesville, kla., assignor to Phillips Petroleum Company, a corporation of Delaware Application December 6, 1954, Serial No. 473,442

13 Claims. (Cl. 196-24) No Drawing.

This invention relatesto improved color and color stability in petroleum distillate. In one of its aspects, this invention relates to a process for improving the color and color stability of a petroleum distillate. In still another aspect, this invention relates tov a process for reducing the sulfur content of a petroleum distillate.

Many refined and unrefined petroleum distillates, and kerosene in particular, contain certain constituents which result in the distillate having an undesirable color ranging from a slight tint to brilliant yellow or orange. The color of a petroleum distillate is defined by the Saybolt color scale wherein the color of +30 is water white. Consumer preference of many distillates such as kerosene is for a water white product and for many purposes, such as in use as a carrier for insecticides, where discoloration of the material with which the insecticidal mixture comes in contact must be avoided, a water white product is ab- ICC dition, improves the color of the distillate; however, the chelating agent alone does not necessarily produce a water White product. The highly adsorbent material also is effective in improving the color of the distillate but, alone, does not produce a water white product under the process conditions employed. The highly adsorptive material is not necessarily effective in stabilizing the color of the product but is effective in reducing the sulfur content of the distillate. Usually, both of these contacting steps are performed; however, in some treatments in which color stabilization is desired but considerable color improvement is not required, only the contacting step with the solutely necessary. Various processes have been developed for improving the color of these off-color distillates and in many of these processes a Water White product is produced. Unfortunately, the. water white product or the product of improved colorp'roduced in some of-the'se processes becomes colored during storage or before use and is not color stable. Very often these refined color unstable products must be further refined in order to obtain a marketable product.

An object of this invention is to provide a process for improving the color of a petroleum distillate.

Another object of this invention is to provide a proc- I ess for producing a color stable petroleum distillate.

Another object of this invention is to provide a process for reducing the sulfur content of a petroleum distillate.

Still other objects and advantages of this invention will be apparent to those skilled in the art upon reading the disclosure and claims.

The present invention provides a process whereby a color unstable petroleum distillate is converted to a color stable product, the color of an off-color distillate is improved, and the sulfur content of a distillate is reduced. An off-color distillate is not only improved in color by the process of this invention but a water White product can also be obtained. The color stability is imparted to a petroleum distillate having color as well as to a Water white distillate by the process of this invention. Unrefined petroleum distillates as well as refined petroleum distillates such as kerosene, fuel oil, jet fuels, naphthas, and gasoline can be treated in this invention to form a low sulfur, color stable product of improved color. The process of this invention is particularly valuable in treating kerosene fractions.

The process of this invention comprises contacting a petroleum distillate under mild conditions with a chelating agent and a solid highly adsorptive material to produce acolor stabilized product of improved color, having reduced sulfur content. The chelating agent is effective in stabilizing the color of a petroleum distillate and, in adchelating agent is used. For example, a distillate refined by a prior art process may be water white but color unstable and only color stabilization by contacting with a chelating agent is necessary. The contacting step with the chelating agent can be carried out either before or after the contacting step employing the highly adsorptive material when both of these contacting steps are used. Preferably, a chelating agent is employed first in the treatment of an oif-color distillate to be improved in color and followed by treatment with a highly adsorptive agent.

As has been indicated, for best results i. e. maximum color improvement and color stability of an off-color distillate, the two step operation is required. That is, the off-color petroleum distillate will have to be contacted by both the chelating agent and the highly adsorptive agent. For many uses, as has been indicated, a water white product is required and in most other applications a water white color, is, at least, desirable. For that reason, the two step operation is a preferred embodiment of this invention. As has been indicated, there are other methods of improving the color and also for lowering the sulfur content. The process of this invention has the distinct advantage over the prior art methods in not only being economical, but stabilizes the color at the same time it upgrades the color rating. 1

Chelating agents are well known in the art and are compounds which form a chelate compound having the same molecule attached to a central atom at two different points whereby a ring structure is formed with at least one such attachment being a coordinate linkage. The preferred type of chelating agent to be employed in this invention is a polycarboxylic amino acid or an alkali metal salt of such an acid; however, this invention is not limited to this particular type of chelating agent. Specific examples of the polycarboxylic amino acids include ethylene diamine N,N-tetra-acetic acid; propylene 1,2- diamine N,N'-tetra-acetic acid; 1,3-diamino propanol-2 N,N-tetra-acetic acid; diethylene triamine N,N-tetraacetic acid; hexamethylene diamine N,N-tetraacetic acid; cyclohexyl amine N-diacetic acid; ethylene diamine N,N'-diacetic acid; and the like. A preferred chelating agent is the tetra sodium salt of ethylene diamine N,N'- tetra-acetic acid. The chelating agent is usually employed in this invention as an alkaline aqueous solution containing 10-75 weight per cent of the solid chelating material; however, chelating agents in the form of a powder or solid can also be used with the addition of water to the distillate being treated.

The term chelate ring describes a cyclic structure that arises through intermolecular coordination in systems containing a donor and acceptor center (such as occurs in salicylaldehyde and the covalent copper salt of glycine) or a ring that is formed by intermolecular coordination in systems that are capable of forming two or more coordinate links, other forms of which are illustrated by the dimers of carboxylic acid O- HO and a variety of metal complexes derived from ethylenediamine or anions of dicarboxylic acids Many unsaturated radicals function as chelate groups partly because of their principle valencies and/or residual affinity, i. e. acetylacetone and oxylate groups and the univalent groups in dimethyl glyoxime.

Acetylacetone HsC-C=O HtJH HaC-JJ=O will chelate copper to form:

HBO-:0 0COH3 HO\ 01 1 /CH 1130-0-0 O=COH: Dimethyl glyoxime HsCC=NOH HaC =NOH will chelate nickel to form:

I CH3 Benzoyl pyruvic acid will chelate beryllium to form:

and benzil monoxime in the alpha form is often used to chelate metals in analytical procedures.

Fiveand six-membered chelate rings are found in the complex amines containing ethylenediamine; triethylenediamine; 1,2,3, triaminopropane; 2,2, bipyridyl; 2 aminomethyl quinoline; 5,15, diaminodiethylamine; ammonia diacetic acid; tripyridyl; etc. For example 1,2,3, triaminopropane will chelate platinum chloride as follows:

HaC-NH:

PtCk

HC-NH1 Hz-NHs I H2 H2 C-N g \i H2N0\ PtCh C-N Hz H2 Polydentate chelate rings may be formed from molecules containing two or more coordinate centers giving rise to diand tri-cyclic systems of the spirane type such as diethylene triamine NHaCHzCHaNI-ICHzCHzNI-Iz and other compounds of the general formula R OHrOHz also 1,2-bis-dimethylarsinobenzene which will chelate nickel to form the following nickel complex:

CH3 CH3 CH3 CH2 In all of the above examples, R may represent alkyl, aryl, cycloalkyl, etc. groups. These groups will generally contain from 1 to 6 carbon atoms since such compounds are generally economically available, however, the invention is not limited to such a number.

The above listing of chelating agents is not intended to be exhaustive but rather is illustrative of the wide variety of chelating agents which are operable in this invention.

The reaction involved in contacting the color unstable, oif-color petroleum distillate with the chelating agents is believed to involve essentially a base exchange between the color bodies in the distillate and the chelating agent to form a chelate compound of the color bodies. The chelate compound formed is very soluble in Water and is removed by washing the distillate with water. The highly adsorptive material is also eifective in removing any minor amount of chelate compound remaining in the distillate.

The highly adsorptive materials are Well known in the art. Such highly adsorptive materials as bauxite, fullers earth, bentonite, montmorillonite, diatomaceous earth and other natural clays have proven to be satisfactory. Acid treated material such as Filtrol clay and other cracking catalysts can be used. Also silica gel, alumina gel, synthetic composite of silica and. alumina,

vantage. I frequently prefer to use cracking catalyst of low activity or spent. catalyst from other refining processes as a low cost source. of highly adsorptive material for use in this invention. Activated charcoal may also be used.

The process of this invention is ordinarily carried out at atmospheric temperature and pressure. Slightly elevated temperature, usually not above 300 or 400 F., can be employed. Elevated pressure is not required but it is desirable to maintain the distillate in liquid phase and pressures as high as 200 p. s. i. or higher can be used. The amount of chelating agent used to treat the petroleum distillate varies and depends upon the concentration of the chelating agent, the petroleum distillate being treated, and the degree of color improvement desired as well as the efiiciency of the contacting operation. The chelating agent is ordinarily used in an aqueous solution of 30-40 weight per cent and in the range of 1-10 volumes of said solution per 100 volumes of distillate. However, stronger or weaker solutions of chelating agents, say in the range of to 75 weightper cent can be used and sometimes greater or smaller amounts will be used.

In the preferred embodiment of this invention, a color unstable, off-color petroleum distillate is first admixed with an aqueous solution of the chelating agent. This admixture is then permitted to separate into an upper distillate layer and a lower aqueous layer containing the water soluble chelate compounds of the color bodies. After removal of theaqueous layer, the remaining color stabilized distillate of improved color and reduced sulfur content is washed with water to remove any remaining chelate compounds. After water washing the distillate is then contacted with a solid highly adsorptive material to obtain maximum color improvement and sulfur removal. The process of this invention can be performed in any suitable manner wherein satisfactory contacting of the chelating agent and the highly adsorptive material with the distillate is obtained. For example, treatment of the distillate by employing contacting of the colorunstable, off-color, high sulfur distillate with a solid highly adsorptive material, first, then followed by treatment with the chelating agent may be used. In this case maximum sulfur removal will be obtained, the amounts varying with the type of adsorptive material used and its inherent properties such as surface area adsorptive activity, etc. Also, the process may comprise either batch or continuous type operations. For example, the chelating agent and distillate may be directly mixed batchwise in a suitable vessel and the aqueous and hydrocarbon phases permitted to separate in the same vessel or the chelating agent and distillate may be contacted in a continuous countercurrent or concurrent operation and the total mixture passed to a separate vessel where phase separation takes place. The contacting of the distillate with the highly adsorptive material may be performed, for example, as either a slurry or percolation type operation.

The advantages of this invention are illustrated by the following examples. The chelating agents, of the polycarboxylic amino acid types, used in these examples were obtained from the Bersworth Chemical Company, Framingham, Mass. These chelating agents are identified as Versene Fe-3 and Versene T and comprise aqueous solu- I tions of ethylene diamine tetra-acetic acid tetra-sodium salt. Versene Fe-3 has a total solids content of 34 percent, specific gravity of 1.2, pH of 11.8 in a one per cent solution, and a light straw color. Versene T has a total solids content of 55.5 per cent, specific gravity of 1.18, pH of 13 in a one per cent solution, and a clear straw color. The petroleum distillate used in these runs was a kerosene taken from the Borger, Texas, refinery of Phillips Petroleum Company. This kerosene had an initial Saybolt color of +2 and a sulfur content of 0.30 weight per cent.

Example I The effectiveness of a chelating agent alone in improving the color of a distillate was determined by shaking a cc. sample of Borger kerosene with 10 cc. of Versene T in a separatory funnel for 5 minutes at room temperature. After phase separation of the kerosene and aqueous fractions, the kerosene fraction was removed and filtered without water washing. The color of the kerosene was improved from a Saybolt color of +2 to +13. In a similar test employing 50 cc. of Versene Fe-3 and 200 cc. of Borger kerosene, color improvement of from +2 Saybolt color to +18 was obtained. After two months dark storage this latter treated kerosene was sampled and color and sulfur content checked. The color was still +18 and the sulfur content was 0.25 per cent.

Example 11 I The effectiveness of a surface active material in the absences of a chelating agent was determined in a test in which 200 cc. of Borger kerosene of +2 Saybolt color was percolated at room temperature through a bed of 15 cc. of spent synthetic silica-alumina cracking catalyst (Filtrol 58) obtained from a cracking unit. The color of the kerosene produced was +26 Saybolt and the color was reduced to +19 after 6 months dark storage in the absence of air. The sulfur content of the kerosene was reduced from 0.30 weight per cent to 0.033 weight per cent. In another run, 200 cc. of Borger kerosene Was percolated through 15 cc. of Sinclair clay, an acidtreated bentonite clay, at room temperature. The color of this kerosene was raised from +2 Saybolt color to +21, and after one hour exposure to sunlight a +16 Saybolt solor was obtained. After 5 months and 15 days of dark storage in the absence of air the color was +12. In a slurry-type treatment, 15 cc. of spent silica-alumina cracking catalyst was admixed with 200 cc. of Borger kerosene of +2 Saybolt color in a separatory funnel. The kerosene fraction was removed, filtered and a color of +24 Saybolt color was obtained. This product was also color unstable since 4 hours exposure to sunlight reduced the color rating to +16 and 5 months and 15 days of dark storage in the absence of air reduced the color rating still further to +10.

Example III The effectiveness of the combined treating steps to produce a color stable, water white product was demonstrated in a test in which 200 cc. of Borger kerosene of +2 Saybolt color was shaken with 20 cc. Versene Fe-3 in a separatory funnel at room temperature. After phase separation the kerosene fraction was decanted, washed with water and percolated through 15 cc. of Sinclair clay at room temperature. The Saybolt color of the filtered product was +30 and the product retained a +30 color after four hours exposure to sunlight. The sulfur content of the kerosene Was reduced from 0.30 weight per cent to 0.099 weight per cent. In another run, 200 cc. of Borger kerosene was admixed with 50 cc. of Versene Fe-3 in a separatory funnel at room temperature and the kerosene fraction was decanted from the aqueous fraction and percolated through 50 grams of spent silicaalumina cracking catalyst. The Saybolt color of the filtered product was +30 and remained +30 after four hours exposure to sunlight. After 5 months and 15 days of dark storage in the absence of air, the color of the product was still +30 and the sulfur content was 0.17 weight per cent.

I have illustrated this invention in one of its preferred embodiments. Those skilled in the art will see many advantages of this invention and will see many modifications which can be made without departing from the scope of this invention.

I claim:

1. A process for improving color and lowering sulfur content of a petroleum distillate which comprises con- A kerosene obtained from the Borger, Texas, refinery of Phillips Petroleum Co.

tacting said distillate with a chelating agent in .the presence of Water and with a highly adsorptive material.

2. A process for improving color and color stability of a petroleum distillate which comprises contacting said distillate with an aqueous solution of a chelating agent.

3. A process for reducing the sulfur content of a petroleum distillate which comprises contacting said distillate with a high adsorptive surface active agent.

4. A process for treating a petroleum distillate which comprises contacting said stream with a chelating agent in the presence of water and separating the resulting treated distillate phase from the resulting aqueous phase containing the water soluble chelate compounds of the color bodies.

5. A process for treating a color unstable petroleum distillate which comprises preparing an aqueous solution of a chelating agent having a concentration of chelating agent in the range of to 75 weight per cent, contacting 100 volumes of said distillate with 1 to 10 volumes of the prepared chelating agent solution, and separating the treated distillate from the resulting aqueous solution.

6. A process for improving color, color stability, and to reduce sulfur content of a color unstable petroleum distillate which comprises preparing an aqueous solution of chelating agent in the range of 10 to 75 weight per cent, contacting said distillate with 1 to 10 volumes of resulting chelating agent solution per 100 volumes of said distillate, contacting this treated distillate eflluent with a highly adsorptive agent, and separating distillate from aqueous solution.

7. A process for improving color and color stability of an ofi colorand color unstable petroleum distillate which comprises contacting-100 volumes of said petroleum distillate with 1 tom volumes of an aqueous solution of a chelating. agent having a concentration in the range of 30 .to 40 weight per cent and separating the treated petroleum distillate from the resulting aqueous solution containing the water soluble chelate compounds of the color bodies. i

8. The process ,of claim 6 wherein the chelating agent is selected from the group consisting of polycarboxylic amino acids and alkali metal salts thereof.

9. The process of claim 7 wherein the chelating agent is'the sodium salt of ethylene diamine N,N-tetra-acetic acid.

10. The process of claim 7 wherein the chelating agent is propylene-1,2-diamine N,N'-tetra-acetic' acid.

11. The process of claim 7 wherein the chelating agent is the sodium salt of 1,3-diamino propanol-2,N,N'-tetraacetic acid.

12. The process of claim 7 wherein the chelating agent is diethylene triamine N,N-tetra-acetic acid.

13. The process of claim 7 wherein the chelating agent is hexamethylene diamine N,N-tetra-acetic acid.

References'Cited in the file of this patent UNITED STATES PATENTS 2,463,015 Bersworth Mar. 1, 1949 2,523,549 Axe Sept. 26, 1950 2,651,595 Moulthrop Sept. 8, 1953 2,659,691 Gilson Nov. 17, 1953 

1. A PROCESS FOR IMPROVING COLOR AND LOWERING SULFUR CONTENT OF A PETRPLEUM DISTILLATE WHICH COMPRISES CONTRACTING SAID DISTILLATE WITH A CHELATING AGENT IN THE PRESENCE OF WATER AND WITH A HIGHLY ADSORPTIVE MATERIAL. 